Reflector arc



M y 1929. L. DEL RICCIO REFLECTOR ARC Filed April 19, 192'? l'zwezz/or.lorenzo. a?! fizlcal'o Mar/26y I Patented May 21, 1929.

UNITED STATES PATENT OFFICE.

LORENZO DEL RICCIO, OF NEW YORK, N. Y., ASSIGNOR TO PARAMOUNT FAMOUSLASKY CORPORATION, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF NEWYORK.

REFLECTOR ARC.

Application filed April 19, 1927. Serial No. 184,854.

This invention has to do with illuminating sources such as are used inmotion picture and other projectors and in other situations where highintensity of illumination is necessary. Although the invention is notneces sarily limited to use in motion picture projectors, its utilityand its inventive objects and corresponding accomplishments may perhapsbe best understood from a consideration of the invention as applied tomotion picture projection.

Various factors have caused desirability of high illumination intensity,and at the same time it is economically desirable to keep down currentconsumption. The most economical form of electric light for the purposeis the arc light; but the intense heat generated in such a light hasoccasioned difliculties. Although arcs equipped with reflectors are nowin use, the large majority of projectors employa condensing lens placedin front of the light. The condensing lens can be somewhat protectedagainst great heat, but it has the disadvantage of receiving only asmall portion of the light generated by the arc. The reflector behindthe light can be made to receive a much larger proportion of thegenerated light, but the reflectors as now commonly in use are exposedto the intense heat and are also exposed to the arc sputter, which,within a short time, necessitates renewal or refinishing of thereflector.

The primary object of this invention is to provide a reflector whichalthough it may be used with any kind of light source, is peculiarlyadapted to use with an arc, the reflector being protected from the heatof the arc and also protected from its sputter. The result of theinvention is the production of an illumination source with which a highintensity of illumination can be attained and which is also veryeconomical of current consumption.

All of this will be best understood from the following detailedspecification of a preferred form and arrangement embodying theinvention, reference for this purpose being had to the accompanyingdrawings, in which:

Fig. 1 is a vertical central section of my improved reflector arc;

Fig. 2 is a rear elevation of the same; and

Fig. 3 is an enlarged detail of parts of the section of Fig. 1.

In the drawings let A designate the are or other source of light.Typicallythis source of light will be an electric arc and typically onecarbon C may project through the parabolic or other shaped reflector Rso that the carbons will present a light obstruction as small aspossible. Assuming that the light source is located at or near thefocusof the reflector surface, the reflector may then be constructed toobtain as wide a light receiving angle as is practicable and yet keepthe source of illumination and heat a little distance in front of thereflector cover-plate P. In practice I-find it perfectly feasible tomake the reflector occupy an angle of about 120 around a source ofillumination, thus giving a light receiving and transmitting surface ofseveral times the effective area of an average condensing lens.

A reflector for projection purposes should form a parallel or nearlyparallel beam of light; and in order to concentrate that beam of lighteither upon a motion picture film or upon an optical system of lenses ofreasonable size, the reflector itself should not be very large. Thatfact and the desirability of making the reflector include a large anglearound the source of light puts the reflector close enough to the sourceof light that, as usually used, the reflector soon becomes deterioratedby the heat and the reflective surface also becomes pitted with thecarbon emanations and sputter of an are.

To overcome these difliculties I provide reflector R with a cover plateP of some suitable material. I prefer a plate of quartz for thispurpose, as it can be placed very close to the are without danger ofsoftening or melting and it is also immune to deterioration by the arcsputter or by the carbon deposit coming from the arc. However, asuitable plate of glass may be used, especially if the glass be ofrather high softening or melting point; and a physically hard glass isto be preferred. Such a glass plate may in time become clouded with adeposit of fine carbon particles, but they can be cleaned off or' a newglass plate substituted very easily.

The glass plate closes the front of the reflector; and in the space thusenclosed within the reflector I pass a ventilating current of somesuitable fluid, either gas or liquid, to keep the reflective face F coolenough to prevent deterioration. I find it fully effective to use air asthe ventilating and cooling fluid. Near its upper and lower edges thereflector may have a series of ventilation openings 10 and ventilationducts 11 are arranged to communicate with those openings. Theventilating air may be put in at the bottom and taken out at the top byany suitable ventilating machine, as for instance by a small blower, theair being moved through at sufficient velocity and therefore insufficient quantity to keep down the temperature of the reflector andalso incidentally to keep down the temperature of cover plate P.

In some cases it may not be necessaryto provide a forced draft throughthe reflector space. If the'heat intensity of the light source is notvery great natural air currents set up by convection upwardly throughthe reflector may be suflicient to carry off, the heat. However, whenusing a high intensity. are I find it desirable to provide artificialdraft. In any case the upper ventilation openings 10 should be largerthan the lower ones, to insure that no large pressure will developbehind plate P and to take care of that expansion of the cooling fluid.I show the upper opening as a slot 10?.

To provide that the carbon C does not come in contact with plate P, thatplate may have a comparatively large opening 20 which may be closed by awasher 21 of mica or other suitable substance. This washer may have acentral opening 22 around the carbon, the size of'the opening, ifdesired,

being gauged to pass a current of air out around the carbon to blow thearc'flame away from the plate.

A reflector protected as I describe iswholv ly immune to any of theusual. .deteriorative influences; and it is therefore unnecessary thatthe initial construction of the reflector itself be limited in the leastby considerations of heat resistivity, the reflector can therefore beconstructed solely with a view to obtaining the highest lightefliciency. 1

Broadly speaking, liquids instead of gases may be used for circulationin the reflector space. Where air or other gas is used as a coolingmedium, the refraction is small enough that it need not be taken intoaccount in the figuring of the reflector, and the cover plate may beplane. But. if it should be desirable to use a liquid as a coolingmedium, as it may be if the reflector were made especially small andplaced very close to a very high powered arc, then the refraction due tothe liquid itself can be offset by a proper compensatory figuring of thereflective surface, or by using a lens shaped transparent plate insteadof the plane plate P.

1. A light reflector comprising a reflective member having a concavereflecting surface, a plate of transparent heat resisting materialcovering the front ofthe reflector, and means for conducting acoolingfluid through the space enclosed by the reflector and said plate.

2. A light reflector comprising a reflective member having a concavereflecting surface, a plate of transparent heat resisting materialcovering the front of the reflector, and means for conducting coolingfluid through the space enclosed by the reflector and said plate, saidmeans comprising ventilation openings near the upper and lower edges ofthe reflector and ventilation ducts communicating with said openings.

3. A light reflector comprising a reflective member having a concavereflecting surface, a" plate of transparent heat resisting materialcovering the front. of the reflector, the

and said plate, said means comprising ventilation openings near theupper and lower edgesof the reflector and ventilation ductscommunicating with said openings.

.5. In combination with an are, a concave surfaced reflector locatedbehind the are, a transparent plate of heat resistant material coveringthe front of the reflector and plate being plane and of uniformthickness,

also located behind the arc, and means for passing .a cooling fluidthrough the space enclosed between the reflector and the plate.

6. In combination with an are, a concave surfaced reflector locatedbehind the arc, a

transparent plate of heat resistant material covering the front of thereflector and also located behind the arc, and means for passing thecooling fluid. through the space enclosed between the reflector and theplate, said means comprising ventilation openings near the upper andlower edges of the reflector.

7. In combination with an'arc, a concave surfaced reflector locatedbehind the arc, a transparent plate of heat resistant material coveringthe front of the reflector and also located behind the arc, and meansfor passing the cooling fluid through the space enclosed between thereflector and the plate, said means comprising ventilation openings nearthe upper and lower edges of the reflector, and ventilation ductsleading to and from said ventilation openings and adapted to direct aforced draft through said reflector enclosed space.

8. In combination with an arc, a concave surfaced reflector locatedbehind the arc, a.

transparent plate of heat resistant material covermg the front ofthereflector and also located behind the arc, and means for passing acooling fluid through the space enclosed between the reflector and theplate, a carbon of the are extending through the plate, and the platebeing provided with an opening around the carbon to pass a fluid streamfor blowing the arc flame away from the plate.

9. In combination with an arc, a concave surfaced reflector locatedbehind the are, a transparent plate of heat resistant material coveringthe front of the reflector and also located behind the arc, and meansfor passing a cooling fluid through the space enclosed between thereflector and the plate, the plate having an opening directing a fluidstream at the arc to blow its flame away from the plate.

10. In combination, a reflector, electrodes adapted to produce an arc,and a transparent plate of heat-resistant material interposed betweensaid reflector and said arc.

11. In combination, a reflector, electrodes adapted to produce an arc, atransparent plate of heat-resistant material interposed between saidreflector and said are, and means for conducting a cooling fluid throughthe space between said reflector and said plate.

12. In combination, a reflector, electrodes adapted to produce an are ata point spaced from the reflector, a transparent plate of heat-resistantmaterial interposed between the arc and the reflector, the space betweenthe plate and the reflector being in communication with the spaceexterior for passage of a cooling fluid through said space between theplate and the reflector.

In witness that I claim the foregoing I have hereunto subscribed my namethis th day of March, 1927.

' LORENZO DEL RICCIO.

